1. Field of the Invention
The present invention is related in general to a hopper car for carrying bulk materials and more particularly to a hopper car gate with a curved door.
2. Description of Related Art
Hopper cars are commonly used to transport bulk materials. Hopper cars include one or more hoppers which hold bulk materials or other cargo for shipment. Each hopper has a discharge opening at its bottom in order to discharge the cargo upon arrival at its intended destination. A gate is joined to each opening to control the discharge of cargo from the hopper. Typically, the gate will have a frame defining an opening and a door moveable between a closed position which blocks the opening and an open position which allows cargo to exit through the opening. An opening mechanism allows a user to move the door between its closed and open positions.
The hopper openings must be spaced a distance sufficient to allow clearance for opening the doors of the gates joined to the openings. Between adjacent hopper openings there are sloped hopper surfaces to facilitate discharge of the cargo within the hoppers. The area beneath the sloped surfaces is wasted space. Reducing the spacing between adjacent hopper openings reduces the wasted space beneath the sloped hopper surfaces, thus increasing the hopper car's carrying capacity. The length or width of hopper cars cannot be increased to increase carrying capacity because there are maximum exterior dimensions to which hopper cars must conform. For example, the Association of American Railroads (AAR) establishes maximum clearance dimensions for all railcars including hopper cars. It is important to maximize a hopper car's carrying capacity while ensuring the car has dimensions within the specified maximum clearance dimensions.
Hopper gate doors must be sufficiently stiff to resist bending from the high pressure exerted on the doors by the cargo contained within the hopper. It is difficult to increase the size of a hopper door, and therefore a hopper opening, without the stiffness of the door being reduced below an unacceptable level. There are a variety of locking mechanisms which are operable to ensure that a door will not open due to impact on the hopper car during transport. These mechanisms increase the complexity and cost of manufacturing a hopper car gate.